I recently changed my tstat due to it going out and the car running too cold. When i changed it i had to take of the camshaft position sensor and that through the timing off so i had a GM stealership re time my engine. Now ever sense i got it back the check engine light will come on only when cars off and key is turned, but once the car is started goes away.

It starts perfectly fine but when engine is cold it seems to have some power loss problem and when i start to drive, sometimes it'll have no power at all but never dies and eventually will run fine. Also seems like once its at normal running temps the power problem goes away. I'm not 100% positive on it completely going away at normal running temps because id rather not keep driving it to find out until i know exactly what going on.

The code is P0300 for random misfire any help???

07 LSJ bone stock besides a injen intake.

 

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I would start with new plugs clean the tb and Maf see if that helps not much info to work from